salty dawg*** revision ***
Reading some of the reviews I think there are a few things that might be said to help others make a decision on this lens like,
1.) They are White Box Lenses i.e. they came from Canon packaged camera kits - Canon sold the EOS-M with the 22 mm or with both the 22mm and the 18-55 zoom
What does this mean? - well the products are the same in manufacturing quality and design - the USA products carry the USA warranty and can be serviced by any authorized USA center vs the Imported that need to be sent out of country for service.
When you consider that Amazon will allow the return of the product in 30 days if say there is a defective issue you need to send it back - after that the seller might take it back if you ask or if not you are on your own - in reality this product is so reliable odds of having an issue are very slim - they will either work perfectly out of the box or they won't - if after a few years it fails (doubtful) just buy another - because the cost of repair would exceed the cost of a new replacement lens at today's selling prices.
2.) Yes the 22mm doesn't have IS and yes, there is some "minimal" distortion - Folks - a 22mm lens is nearly what is considered as a fish eye lens so that's normal for any 22 mm lens no matter the price point or manufacturer and totally correctable in Photoshop or other editing software.
3.) There is a lens shade for this lens - $10.00 on Amazon - get it.
4.) Be advised some of the cameras and lenses are Imported vs USA models - there is fine print listed covering this - it's not really a big deal given the cost of these cameras and that the 30 day Amazon return option will cover you as most will either be DOA or last for normal service intervals.
I have another take on if you should get the M lenses or use your glass - here's mine, I bought both of the M lenses even though I have nearly every L glass Canon makes up to the 300 mm F2.8 Prime so I have a big $ investment in L glass and I did buy the adapter however, I'm not going to use my L glass for everyday shooting on this camera - that would defeat the reason for a small camera and putting my L glass in harms way by dragging it around in the car or what ever - forget it - the kit lenses are very acceptable in terms of sharpness and overall performance ie. speed, clarity, color rendering, etc. so for a camera and lens arrangement for everyday use and go in harms way that's why I went with the kit lenses. now if I decide to do some serious stuff with the small base unit because of the size and weight savings I can drag out the L glass and have at it - I like options.